WFDC2 and Pleural effusion: For tissue-specific biomarkers, TMPRSS3 (transmembrane serine protease 3), NAPSA (napsin A aspartic peptidase), and DSP (desmoplakin) were identified from pleural effusion BL tumor cells, while APOE (apolipoprotein E), COX6C (cytochrome C oxidase subunit 6C), and WFDC2 (WAP 4-disulfide core domain 2) were identified from liver BL tumor cells (Fig. 2K).